Some people like to browse Pixiv for sexy art by Japanese artists. However, the overwhelming majority of content on Pixiv is described, and tagged with Japanese words. So searching for a tag in English will not yield many results.
So, here is a list of Japanese words you can use to search Pixiv for content you enjoy.
へんたい - Hentai (This tag is not necessary for pictures tagged R-18 or R-18G)
無修正 - Uncensored (specifically refers to lack of mosaics or bars over genitals)
エッチ - Ecchi (Pervy, but not outright pornographic)
落書き - “Rakugaki.” Scribble/sketch.
原創 - Original (Your own characters/setting, not from a franchise or anime)
アナログ - Analog (Specifically refers to piece not being digital)
ファンタジー - Fantasy (Genre. Swords and Sorcery, etc)
やおい - Yaoi (male/male sexual situations)
少年愛 - Shounen Ai (male/male, but more emotional than sexual)
薔薇 - Bara (Male/Male, but much more masculine. Generally involves burly, muscular characters)
ホモ - Homosexual (usually more masculine. Lit. “Homo”)
ケモノ - Kemono, Furry (lit. “Beast Person”)
ケモホモ - “Kemohomo,” gay furry
NOTE: I have noticed that there doesn’t seem to be any notable tags for hetero/straight-oriented art, as this is considered the “default” type of hentai.
姫 - Hime/Princess (Young lady of high birth, not necessarily royalty)
筋肉娘 - Muscle Girl (kinniku musume)
長身女性 - Tall girl (Chõshin josei)
少年 - Boy (“Shonen.” Refers to young male characters, from childhood to age 18. Teenager.)
男の子 - Boy (similar meaning to above)
青年 - Young Man (“Seinen,” term for young adults)
美少年 - “Handsome youth.” Characters who are implied to be as such, in-universe.
巨根 - Big penis (“kyokon,” usually on explicitly masculine subjects. Bara, etc)
包茎 - Uncut penis (lit. “Phimosis”)
男の娘 - Femboy/Trap (Otokonoko, lit. “girl-boy”)
女装 - Crossdressing/Drag (specifically, males crossdressing as females)
射精 - Ejaculation (“Shasei,” the act of shooting sperm)
ペニス - Penis (referring to the actual body part)
ふたなり - Futanari (Hermaphrodite, has both genitals)
ふた×男 - Futa on Male (literally “futa x male”)
ニューハーフ - Newhalf (Japan’s term for “Transexual” or “Shemale.” Breasts, dick, balls, but no vagina)
ボンデージ - Bondage (katakana)
調教 - Torture (lit. “breaking”)
ラバースーツ - Rubber/Latex bodysuit
縛り - Shibari (Rope bondage)
緊縛 - Bondage (“kinbaku,” advanced rope bondage)
くすぐり - Tickling (lit. “Feathers”)
レイプ - Rape/forceful sex (katakana version)
身体に落書き - Body writing (Things written/drawn on skin)
拘束 - Restraint (cuffs, ties, cloth, shackles, etc…)
メス豚 - Sow/female pig (BDSM context)
正の字 - Positive/Happy character (As opposed to distressed, usually in a BDSM context)
フェムドム - Femdom (katakana)
マミフィケーション - Mummification (katakana, fetish involving full body restraints with tape, strips of cloth or other materials)
機械姦 - Fucking Machine (Kikaikan)
溢れ精液 - Overflowing semen (as in, leaking out of a recipient)
ボテ腹 - Botehara (distended belly)
ダブルピース - Double-Peace (Making “peace” sign with each hand)
まんぐり返し - Piledriver (sexual position, legs WAY back behind head)
逆アナル - Pegging, anal penetration of a male by female or futa (lit. “Reverse Anal”)
フェラチオ - Fellatio (katakana)
クンニリングス - Cunnilingus (katakana)
精液 - Cum (referring to the actual semen itself)
フィストファック - Fisting (katakana)
ニプルファック - Nipple Fuck (katakana)
逆レイプ - Reverse Rape (wherein females force themselves upon unwilling men)
ペニバン - strapon dildo (”peniban”, same as above, but as a more japanese term)
中出し - Nakadashi (creampie)
アヘ顔 - Ahegao (literally “idiot face”, an over-the-top silly expression for excessive pleasure)
ボコォ - Belly bulge (bulging or deformation of the belly by a mass)
腹ボテ - Belly Bulging (inflation of the belly to any degree by fluids)
尻 - Butt (shiri, more like the butt itself, the glutes but without exposing the asshole)
お尻 - Ass (refers to the actual exposed anus)
レスリング - Wrestling (katakana)
CLOTHING / COSTUME / APPEARANCE:
下着 - Underwear (Lingerie)
褐色 - Dark Skin (lit. “Brown”)
王女 - Ojo/Princess (lit. “King’s Daughter”)
MONSTER / RACE / COSTUME:
宇宙人 - Alien (lit. “Person from Space.” This is not the same as “gaijin”)
エイリアン - Alien (same meaning, but in katakana)
マイリトルポニー - My Little Pony
異種間恋愛 - Interspecies Romance
異種姦 - Interspecies sex (Human x Non-human, animal, fantasy creature, etc)
モンスター娘 - Monster girl (usually humanoid in general shape)
ネコミミ - Nekomimi (Catgirl)
ドラゴン - Dragon (As depicted in western mythology)
女戦士 - Female Warrior (Onna Senshi)
レスラー - Wrestler (katakana)
着ぐるみ - Pyjama-style costume. (Sort of like a fursuit, but looser. May or may not show the person’s face)
バーコード - Bar Code (on skin)
王女 - Ojo/Princess (lit. “King’s Daughter”)
性転換 - Gender Swap (Male becoming an actual female, or vice versa)
ふたなり - Futanari (hermaphrodite, dickgirl, shemale, etc)
合体 - Absorption, Merging (lit. “Coalescence”)
捕食 - Vore (lit. “Predation”)
丸呑み - Vore (Marunomi) Swallowed Whole
体格差 - Size difference (Karada kakusa)
筋肉 - Muscle (kinniku, can be used to tag muscled characters
Feel free to reblog with any tags I may have missed.
